Yahya related to me from Malik from Hisham ibn Urwa from hisfather that Hamza ibn Amr al-Aslami once said to the Messenger ofAllah, may Allah bless him and grant him peace, "Messenger of Allah, Iam a man who fasts. Can I fast when travelling?" The Messenger ofAllah, may Allah bless him and grant him peace, said, "If you want youcan fast, and if you want you can break the fast."
USC-MSA web (English) reference: Book 18, Hadith 24
Arabic reference: Book 18, Hadith 658